George and Lennie are like family. They are companions. George had promised Lennie's aunt that he would take care of Lennie. George is true to his word. George claims that the two of them would be lonely without each other:
Guys like us, that work on ranches, are the loneliest guys in the world. They got no family. They don’t belong no place. . . . With us it ain’t like that. We got a future. We got somebody to talk to that gives a damn about us.
George and Lennie have a bond as they migrate from ranch to ranch. Lennie is often found in trouble; therefore, George has to take Lennie and run to another location. Truly, George gets frustrated with Lennie, but he continues to support Lennie, even when he gets in trouble. George needs Lennie as much as Lennie needs George.
George and Lennie dream together. They dream of having their own farm one day. This dream keeps them going. Lennie asks George to repeat the dream of having their own farm. George does so. He repeats the dream of having a farm with a garden and rabbits for Lennie to tend to. Is is a beautiful dream.
No doubt, shooting Lennie is the most difficult decision George has to make. Even in death, George is showing how much he cares about Lennie. George does not desire for Lennie to be hung at the hands of Curley. George prevents Lennie from suffering when he shoots him. Of course, George will be one of the loneliest guys in the world without Lennie. His will to dream is over:
When George is driven to shoot Lennie after Lennie accidentally kills Curley's wife, he destroys his own dream, too. Its fulfillment is doomed by insensitive materialists. Along with the destruction of his dream, George loses the chance to become a better man.
Lennie made George a better man.